New Prius Prime owner in Massachusetts (looking for local installers)

You will have to find someone who is not a professional. Any credible shop will not disable a working safety device that is mandated by law. It's against a law and they can get in trouble.

 

I go visit my family/friends in Boston often but don't live close. I haven't tried on mine to see how hard it is to get to the speaker, but permanently disabling the sound without causing the error message to appear on the dash seems to take a bit of manipulation.
See this thread: Disabling the prius prime noise maker. | PriusChat

Plus, since this is now a law, it is plausible that future state auto inspection may check on this device and if that happens, you will have to fix it before you can get the sticker. To avoid the hassle, it would be better to be able to turn on and off the sound at will. That seems to take more work and some engineering. At present, the spaceship sound does not bother me too much, so I may just let it go.

 

I don't know any recommendations for your local shops, but I am sure you should be able to find a soundproof installer. Here, many car audio installers do such works.

If you are looking for a DIYer to help you, this thread should help. Prius Prime detailed sound proofing procedure. | PriusChat

 

Is the spaceship noise worse in the later models? I don't notice it in my 2017 Prime, even when I have no music and windows rolled down.

 

Yes, starting from the 2021 model, the VPNS (aka noisemaker) is noticeably louder than previous models, especially in reverse. I never noticed the VPNS sound in my 2017 PP nor in my 2020 PP even though I had them set at the highest volume by customization using Carista. And it is no longer owner customizable in 2021 and newer models.